Process of catalytically combining gases



A. HENWOOD.

PROCESS OF CATALYTICALLY COMBINING GASES.

APPLICATION FILED JAN. 9, 1919.

l ,347, 1 60. Pat nt d uly 20, 1920.

I UNITED STATES- PATENT OFFICE.

PROCESS OF CATALYTICALLY COMBINING GASES.

Original application filed July 8-, 191a,

To all whom it may concern:

Be it known that I, ABRAHAM Hnnwooo, a citizen of the UnitedStates, residing at Cynwyd, countyof Montgomery, and State ammonia gas and oxygen through such catalyzer. In the same application, and also in i .an application filed January 9, 1919, Serial No. 270,409 (which is another division of said application Serial No. 243,758) I have described a method of maintaining the temperature at the point of reaction within the range of efficiency and safety by gas control, preferably by excess of oxygen, to maintain the temperature relatively low, and by applying heat by an outside thermostaticallycontrolled electrical means, to maintain the temperature of reaction above the lowest range of permissible temperature to secure maximum concentration of nitric acid but not sufficiently high to permit any substantial decomposition of nitric acid. In said application Serial No. 243,758, I have also described, as a part of the process, the passage of the mixture over or through a cataly zer carrier while'maintaining the carrier flexibly supported to provide for its expansion or contraction under the influence of. The last named temperature. variations. feature of the process forms the subject-matter of the present application.

In the description of the process of the present application, it will be advisable to referfto these other features of the general process, although no claims are herein inade thereto.

In carrying out the present process I prefer to pass the oxygen and ammonia gas over or through a continuous porous or permeable contact or reaction surface, or diaphragm,-of catalytic material, preferably platinum sponge, the massof catalytic material being so small as not to be self-sustaining but distributed uniformly over the Specification of Letters Patent.

' other suitable shape.

Patented July 20,1920.

Serial no. 243,758. Divided and this application filed January 9,

Serial No. 270,410.

surface of a porous or permeable material which is preferably non-metallic, non-catalytic, and a poor conductor of heat.

A base or support of such material of any suitable shape, so covered with a coating, film or'diaphragm of platinum, is placed in the channel provided for the reaction gases so that the latter must pass over or through the same and hence be brought into reactive contact with the continuous surface of platinum. Thus I attain maximum economy, even distribution, minimum mass and uniform temperature, and insure that practically every molecule of the reaction gases will be subjected, and in the same degree, to the influence of the catalyzer.

In preparing the catalyzer, I take a support, which is preferably in the shape of a disk or hemisphere, but which may have any The support is of porous or permeable material, such as alundum or silica. The catalytic material, preferably platinum, is deposited, formed or placed, on either or both surfaces of the support, but-preferably only on one surface. The catalytic material may be applied in various ways, but I-prefer to soak an alundum support in ammouium chlorid, dry it, remove any excess from the surface, spray upon the surface a platinum chlori'd solution, thereby forming on the surface a precipitate of ammonium chlorplatinate, and then dry and ignite, thus burning off or volatilizing ammonia, hydrogen chlorid, steam and chlorin, and leaving a superficial layer of platinum sponge. The carrier and catalyzer are then so placedin the reaction chamber that the gases of reaction are compelled to pass through both the'diaphragm of platinum sponge and the support or carrier therefor.

To secure a fine and certain adjustment of the temperature, I use suflicient excess oxytures, and then add heat from outside, by

automatically-controlled, and preferably thermostatically-controlled, means to maintain the temperature safely above the lower limit of the ran e of permissible temperatures, thereby 0 setting what would otherwise be objectionable depressions of temperature below that at which the reaction takes place advantageously. The heating may be' imity to the catalyzer and also to a thermostatic'element which is connected to, and

, operates, a rheostat controlling the flow of electric current, so as to cut out resistance as the temperature decreases and introduce resistance as the temperature increases and break the circuit altogether at any desired upper limit of temperature.

hile, in the practice of the process, the the temperature, during the reaction process, is maintained fairly even, it is clear that when the process is discontinued, there is a very considerable fall in temperature, and that when the process is again renewed, there is a corresponding great rise in temperature. The result is that the carrier expands and contracts, and it is obvious that, by reason thereof, if the catalytic diaphragm and its carrier were fixedly anchored, serious difliculties would be experienced in carrying out the process, for the reason that the alunvariation of temperature at the beginning and end of a run, the edge of the support may be sustained 1n a, groove containing a plastic lute, composed of a vitreous substance of the proper degree of viscosity at the working temperature, and which is chemically inert to the reaction gases, thereby provld'ing a hermetlcal seal Which allows the support to expand as 1t is heated and contract as it is cooled. I prefer to use a sustaining seal or late composed of boric acid. It is this feature of the process which forms the subject-matter of the present application. 7

While the practice of the process does not depend upon the employment of any particular apparatus, the devices illustrated in the accompanying drawings may be used to carry out the process.

Figure 1 is a diagram of that part of the apparatus which may be convenientlycalled the reaction chamber, including the thermostatically-controlled outside heating means. Fig. 2 is a similar View of a 'modificatlon with outside heating means omitted.

In Fig. 1, a and b are two sections of a tube or chamber into which the gases of re action pass and combine to form nitric acid. The tube, at the junction of the two sections, is bent circumferentially to form a circumferential groove 0 containing boric acid 01 or some equivalent substance that is plastic,

-v1treous, vlscous and chemically inert to the gases. Thedisk-shaped support 6 composed y) f l a, hold1ng distributed ove its surface, in a continuous manner, plat- V mum sponge f, has a dependlng peripheral flange g resting in the groove 0 and embedded in the plastic lute d, which, while providing a hermeticalseal, allows the disk 6 to expand and contract. he support is either inherently porous or is provided with perforations which permit the free flow therethrough of gas and acid It is also and to retain the heat from the reaction taking place at thls polnt.

resistance wire winding it incloses the rests in the inner groove 9. A cover a, of pyrex glass, overlies and surrounds, and is spaced from, the support t and rests in the groove 9. An outlet pipe '0 for the product of the reaction extends through the base r and communicates with the space'between the cover u and the support if. A hood or deflector w is placed over the mouth of the inlet pipe s-to distribute the entering gases within the chamber inclosed by the support t preparatory to their passage through the cup. The lower edge of the cup t, resting in the groove 79, is embedded in a plastic lute w of boric acid or other suitable material. I prefer to flow the boric acid over the surface of the base r so that it will fill and overflow the grooves and provide a protective covering or enamel for the bottom of the reaction chamber.

do not herein claim the catalyzer and support therefor, nor the process of catagas to form nitric acid by passing the mixture through said catalyzer, nor the process of regulating the temperature of reaction.

or do I claim the apparatus herein described for carrying out the process herein claimed. These other; inventions form the separate applications, namely Serial No. 243,758, filed July 8, Serial No. 241,724, filed June 25, 1915; and Serial No. 270,409, filed January 9, 1919. 4

Having now fully described my invention, what I claim and desire to protect by Letters Patent is:

1 The improvement in the art of catalytically combining gases which consists in passing a mixture containing the gases to be combined over a catalyzer supported upon a carrier, and supporting the carrier flexibly to provide for its expansion and contraction under the influence of temperature variations.

2. The improvement in the art of catalytically combining gases which consists in passing a mixture containing the gases to be comblned over a catalyzer supported upon a carrier, and applying. in supporting relation to the carrier, a plastic viscous material to yieldingly allow the carrier to expand or contract under the influence of temperature variations.

In testimony of which inventionI have hereunto set may hand, at Gynwyd, on this 26th day of December, 1918.

ABRAHAM HENWOOD. 

